Car super sensitive to ambient temperature

[astat1]

My 428CJ runs great at night or when cool outside, but if its 90, sunny and I get to many red lights the heat goes up. My gauge never reads more than 3/4 hot, and I never "boil over". My car idles, misses and dies, needing 30 minutes to cool. I advanced the timing. Could it be a vacuum problem? Thanks.

[Neil Bierman]

Have you checked the ignition coil? Many times they fail when they get hot. I read on one website where a guy rigged up his windshield washer system to spray water on the coil to troubleshoot the system. He ran the car until it stalled out. Then he hit the windshield washer, spraying cool water on the coil. The car started right up. That confirmed for him that he had a bad coil.